1. Field of the Invention
This invention relates to a system for compensating for spatial errors caused between a space of command and a space of motion in a movable machinery having a three-dimensional spatial mechanism, for example, a three-dimensional coordinates measuring machine, a machine tool or a robot.
2. Description of the Related Art
In the movable machinery having a three-dimensional spatial mechanism, working errors may occur in the components constructing the movable machinery or deformation and/or strain due to temperature variations may occur in the components. When the above working errors, deformation and/or strain due to temperature variations occur, a space of motion in which the movable machinery actually moves does not correspond to a space of command for controlling the movement of the movable machinery. In order to solve the above problem, the spatial error compensation technology for compensating for spatial errors between the space of motion and the space of command is constructed by use of adequate algorithms of arithmetic. Particularly, various spatial error compensation techniques relating to the three-dimensional coordinates measuring machine (CMM) have been put to practice and the basic technology thereof has been developed in various manners.
In a case where the spatial error compensating system is mounted on the CMM, it is necessary to consider the requirement of the users that measured data (real data) obtained as a result of compensation for spatial errors between the space of command and the space of motion can actually be output from the CMM and the real data thus output can be processed.
It is also necessary to move the probe of the CMM to a given command position on a compensated space or the space of motion which has been compensated by the spatial error compensation technology. In this case, it is necessary to provide a reverse compensation system for correcting a commanded value on the space of command to match with the space of motion (compensated space) by use of a reversed function of a compensatory function used for compensating the measured value.
However, the conventional method which requires different functions for effecting the above spatial error compensation and the motion control on the compensated space necessitates two systems of function generators, and therefor, the function generating process will become redundant. Particularly, since most of the reverse functions of the compensatory functions are multiple-valued functions, the process in the reverse function generator will become complicated.